The present invention relates to a method and apparatus for positioning a tapered member to verify the accuracy of the taper.
When machining and grinding a shaft having a continuous taper it is desirable to provide a simple and convenient apparatus for checking or verifying that the shaft has been ground smoothly to the proper angle of taper. This is particularly true when providing tapered shafts for tool shanks whose use requires that they be machined within very close tolerances. Various prior art devices have been proposed to measure or check the taper of a shaft or a bore hole. However, none of these prior devices has been found to be a simple and efficient as desired for use on a regular basis when producing a large quantity of tapered shafts.
On such prior device is disclosed in U.S. Pat. No. 2,551,471 issued to Snow. The Snow patent discloses a gauge comprising a block provided with a laterally extending top portion and an upwardly curved portion adapted to follow the outer contour of a tapered bearing race. When the tapered bearing race has been placed in the block, a pair of feeler pads attached to a pair of spaced apart gauges are lowered until they contact the surface of the bearing. The feelers simultaneously impart their position to the respective indicating fingers on a single calibrated dial face. If the indicating fingers are both within a predetermined tolerance range, the diameters of the tapered bearing race are acceptable. A further scale is provided to determine the spacing between the two indicating fingers. A device of this type would require a relatively complex set of rods and gears in order to compare the relative positions of the two indicating fingers on the single dial face. In addition, the machining of the support block would be difficult since the block itself comprises a portion of a tapered bore.
U.S. Pat. No. 3,845,567 issued to Johnson discloses a device for checking the taper of a keyway in a bore. The device comprises a fixed tapered surface which limits the movement of the device into the keyway and a second movable tapered surface. By sliding the second surface into the keyway it can be determined if the taper of the keyway is too large or too small. A device of this type, however, could not be used to determine whether the outside taper of a shaft were ground to the proper dimensions.
Other prior art devices ae disclosed in U.S. Pat. No. 3,115,705 and 4,106,205 issued to Whiteman and Wiederkehr, respectively. The Wiederkehr patent relates to an apparatus for measuring inside and outside chamfers on work pieces but a device of this type could not verify an elongate taper of a shaft. The Whiteman patent teaches a gauge for measuring the angle of a tapered face of a work piece by precisely measuring tangent quantities of inclinations, but a device of this type could not be employed for relatively rapid measurements.
Accordingly, it is an object of the present invention to provide a method and apparatus for positioning a tapered member to verify the taper in a simple, efficient and rapid manner.
A further object of the present invention is to provide a method and apparatus which positions and verifies the taper of a member along its entire length without involving a resetting of a gauge or a changing of the position of the shaft.
A still further object of the present invention is to provide an apparatus which is readily adaptable to verify the taper of members of different diameters.
These and other objects are accomplished according to the present invention by providing an apparatus for use with a gauge which comprises a first surface and a second surface having an angle relative to a longitudinal axis of the first surface equal to one half the included angle of the taper of the member to be measured arranged along one side of the first surface. A tapered surface of the tapered member is positioned against the first and second surfaces and, if the tapered surface corresponds to the desired taper, a longitudinal axis of the first surface is coplanar with a centerline of the member and a portion of the tapered surface remote from the first surface is disposed at a preselected level.
In a preferred embodiment, the apparatus is arranged horizontally and a plurality of horizontal gauge block surfaces are arranged at predetermined vertical heights with respect to a base of the first surface. A plurality of gauge blocks are provided whose size is determined by the largest diameter of the particular member or shaft to be verified. An appropriate gauge block is placed on an appropriate gauge block surface so that a dial indicator can be preset to zero with reference to an upper, horizontal gauge surface of the gauge block.
In operation of the present invention, the tapered member to be verified is placed against the two angled surfaces. The dial indicator, after having been preset to zero on the appropriate gauge surface, is then placed at various locations on an upper portion of the tapered surface along the length of the member to obtain a reading. These readings are compared with the preset zero reading obtained at the appropriate gauge surface to determine whether the taper has been properly ground and machined. If the dial indicator reads zero at the various locations along the member, the member has been ground to the proper taper.
In a further preferred embodiment of the present invention, a rest button is arranged beneath an edge of the first surface against which a flange on the tapered member is placed. Also, by verifying that the tapered surface is accurately ground at both ends thereof, the gauge line to flange dimension is also verified by the present invention.
A further preferred embodiment of the present invention, includes a spacer block which redefines the second surface along the first surface to allow the taper of smaller diameter members to be verified in the apparatus. Also, a relief is cut in the first surface in order to receive a cylindrical end of a shaft and to assure that portions of the tapered surface of the member lie flush against the two surfaces.